Nicki Minaj has allegedly threatened to 'knock out' Mariah Carey on the set of American Idol.

The singers, who reportedly do not get along, were said to have caused production to stop during auditions in Charlotte, North Carolina on Tuesday (October 2) over an argument which is thought to have stemmed from a contestant's performance.

In a clip obtained by TMZ, Minaj appears furious as she shouts at Carey, saying: "I told them, I'm not f**kin' putting up with her f**kin' highness over there."

Sources told the site that the 'Super Bass' rapper also told Carey that she was going to "knock [her] out", though the comment - which was was not caught on tape - was apparently made before the video starts.

While American Idol producers have previously denied claims of a feud between the superstars, as has Carey herself, showrunners are now said to be worried about their ability to get along throughout the season.

It was reported last month that Carey and Minaj had called a "truce", after agreeing that fighting would not be good for American Idol viewers.

Watch video of Nicki Minaj's reported outburst against Mariah Carey on the American Idol set below: